JP2021163768A - Protective sheet for semiconductor processing and method for manufacturing semiconductor device - Google Patents

Abstract

To provide a protective sheet for semiconductor processing, capable of sufficiently following the irregularities of a wafer and capable of suppressing the occurrence of chip cracks after grinding, while an adhesive residue is suppressed in separation, even when a semiconductor wafer having irregularities due to DBG and the like is processed thinly.SOLUTION: There is provided a protective sheet for semiconductor processing which includes a base material, and an intermediate layer and an adhesive layer on one main surface of the base material, in this order. The intermediate layer and the adhesive layer are energy ray curable, and the Young's modulus of the protective sheet for semiconductor processing at 50°C before energy ray curing is 600 MPa or more.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device. In particular, a protective sheet for semiconductor processing, which is suitably used for a method of grinding the back surface of a semiconductor wafer having irregularities and individualizing the semiconductor wafer by the stress or the like, and a semiconductor device using the protective sheet for semiconductor processing. Regarding the manufacturing method.

As various electronic devices are becoming smaller and more multifunctional, the semiconductor chips mounted on them are also required to be smaller and thinner. In order to reduce the thickness of the chip, it is common to grind the back surface of the semiconductor wafer to adjust the thickness. Further, in order to obtain a thinned chip, a groove having a predetermined depth is formed from the front surface side of the wafer by a dicing blade, and then grinding is performed from the back surface side of the wafer. A construction method called a dicing method (DBG: Dicking Before Grinding) may be used. In DBG, since the back surface grinding of the wafer and the individualization of the wafer can be performed at the same time, a thin chip can be efficiently manufactured.

Conventionally, when grinding the back surface of a semiconductor wafer or manufacturing a chip by DBG, an adhesive tape called a back grind sheet is attached to the wafer surface in order to protect the circuit on the wafer surface and hold the semiconductor wafer and the semiconductor chip. It is common to do.

As the back grind sheet used in the DBG, an adhesive tape having a base material and an adhesive layer provided on one surface of the base material is used. As an example of such an adhesive tape, Patent Document 1 and Patent Document 2 provide a base material having a high Young's modulus, a buffer layer provided on one surface of the base material, and an adhesive layer provided on the other surface. Adhesive tape is disclosed.

In recent years, as a modification of the pre-dicing method, a method has been proposed in which a modified region is provided inside the wafer by a laser and the wafer is individualized by stress during grinding of the back surface of the wafer. Hereinafter, this method may be referred to as LDBG (Laser Dicing Before Grinding). In LDBG, since the wafer is cut in the crystal direction starting from the modified region, the occurrence of chipping can be reduced as compared with the pre-dicing method using a dicing blade. As a result, a chip having excellent bending strength can be obtained, and it is possible to contribute to further thinning of the chip. Further, as compared with DBG in which a groove having a predetermined depth is formed on the surface of the wafer by the dicing blade, the yield of chips is excellent because there is no region for scraping the wafer by the dicing blade, that is, the calf width is extremely small.

On the other hand, when a multi-pin LSI package used for MPU, gate array, etc. is mounted on a printed wiring board, a convex electrode (bump) made of eutectic solder, high temperature solder, gold, etc. is used as a semiconductor chip on the connection pad portion. ) Has been formed, and a flip chip mounting method has been adopted in which these bumps are brought into face-to-face contact with the corresponding terminal portions on the chip mounting substrate and melted / diffused joined by a so-called face-down method. ..

International Publication No. 2015/156389 Japanese Unexamined Patent Publication No. 2015-183008

The semiconductor chip used in this mounting method is obtained by fragmenting a semiconductor wafer having irregularities such as a semiconductor wafer on which convex electrodes are formed. Even when a semiconductor wafer having such irregularities is ground by DBG, as described above, the circuit surface of the semiconductor wafer is used to protect the circuit surface during grinding and prevent chip movement after the wafer is fragmented. A back grind tape is attached to the.

However, when the backgrinding tapes described in Patent Documents 1 and 2 are attached to the circuit surface of a semiconductor wafer having irregularities and ground by DBG, the backgrinding tapes described in Patent Documents 1 and 2 are used. There are problems that the unevenness of the semiconductor wafer cannot be sufficiently followed, water infiltrates the circuit surface during grinding, and the chip moves (chip shift) after the wafer is fragmented. Further, in such a back grind tape, when a soft intermediate layer is provided in order to deal with the unevenness, the unevenness can be followed, but when the back grind tape is peeled from the semiconductor wafer, glue is applied to the convex electrode. There was a problem that the rest would occur.

The present invention has been made in view of such an actual situation, and even when a semiconductor wafer having irregularities is thinly processed by DBG or the like, the irregularities of the wafer can be sufficiently followed, cracks of chips after grinding can be suppressed, and cracks of chips can be suppressed. It is an object of the present invention to provide a protective sheet for semiconductor processing in which adhesive residue is suppressed at the time of peeling.

Aspects of the present invention are as follows.
[1] A protective sheet for semiconductor processing having a base material and an intermediate layer and an adhesive layer on one main surface of the base material in this order.
The intermediate layer and the adhesive layer are energy ray curable and
A protective sheet for semiconductor processing in which the Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50 ° C. is 600 MPa or more.

[2] The protective sheet for semiconductor processing according to [1], which has a buffer layer on the other main surface of the base material.

[3] The protective sheet for semiconductor processing according to [1] or [2], wherein the Young's modulus of the base material is 1000 MPa or more.

[4] The protective sheet for semiconductor processing according to any one of [1] to [3], wherein the thickness of the intermediate layer is 60 μm or more and 250 μm or less.

[5] In the step of grinding the back surface of a semiconductor wafer having grooves formed on the surface of the semiconductor wafer and separating the semiconductor wafer into semiconductor chips by the grinding, the semiconductor wafer is attached to the surface of the semiconductor wafer and used [1]. ] To [4]. The protective sheet for semiconductor processing.

[6] A step of attaching the protective sheet for semiconductor processing according to any one of [1] to [5] to the surface of a semiconductor wafer having irregularities, and
A step of forming a groove from the front surface side of the semiconductor wafer, or a step of forming a modified region inside the semiconductor wafer from the front surface or the back surface of the semiconductor wafer.
A process in which a semiconductor wafer on which a protective sheet for semiconductor processing is attached to the front surface and a groove or modified region is formed is ground from the back surface side and separated into a plurality of chips starting from the groove or modified region. When,
This is a method for manufacturing a semiconductor device, which comprises a step of peeling a protective sheet for semiconductor processing from an individualized semiconductor chip.

According to the present invention, even when a semiconductor wafer having irregularities is thinly processed by DBG or the like, the irregularities of the wafer can be sufficiently followed, cracks of chips after grinding can be suppressed, and adhesive residue can be suppressed at the time of peeling. It is possible to provide a protective sheet for semiconductor processing.

FIG. 1A is a schematic cross-sectional view showing an example of a protective sheet for semiconductor processing according to the present embodiment. FIG. 1B is a schematic cross-sectional view showing another example of the protective sheet for semiconductor processing according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing a state in which the protective sheet for semiconductor processing according to the present embodiment is attached to the circuit surface of the semiconductor wafer.

Hereinafter, the present invention will be described in detail with reference to the drawings based on specific embodiments. First, the main terms used in the present specification will be described.

Fragmentation of a semiconductor wafer means dividing a semiconductor wafer into circuits to obtain a semiconductor chip.

The "front surface" of a semiconductor wafer refers to a surface on which circuits, electrodes, etc. are formed, and the "back surface" refers to a surface on which circuits, etc. are not formed.

DBG refers to a method in which a groove having a predetermined depth is formed on the front surface side of a wafer, then grinding is performed from the back surface side of the wafer, and the wafer is fragmented by grinding. The groove formed on the surface side of the wafer is formed by a method such as blade dicing, laser dicing or plasma dicing.

The LDBG is a modification of the DBG, and refers to a method in which a modified region is provided inside the wafer by a laser and the wafer is individualized by stress during grinding of the back surface of the wafer.

The “chip group” refers to a plurality of semiconductor chips held on the semiconductor processing protective sheet according to the present embodiment after the semiconductor wafer is fragmented. As a whole, these semiconductor chips have a shape similar to that of a semiconductor wafer.

In the present specification, for example, "(meth) acrylate" is used as a term indicating both "acrylate" and "methacrylate", and the same applies to other similar terms.

The "energy ray" refers to ultraviolet rays, electron beams, etc., and is preferably ultraviolet rays.

(1. Protective sheet for semiconductor processing)
As shown in FIG. 1A, the protective sheet 1 for semiconductor processing according to the present embodiment has a structure in which an intermediate layer 20 and an adhesive layer 30 are laminated in this order on a base material 10.

The protective sheet for semiconductor processing according to the present embodiment is used by being attached to a semiconductor wafer having irregularities. Examples of the semiconductor wafer having irregularities include a semiconductor wafer on which convex electrodes are formed.

For example, as shown in FIG. 2, the protective sheet 1 for semiconductor processing according to the present embodiment has an adhesive on the bump forming surface 101a of the semiconductor wafer with bumps in which the bumps 102 as convex electrodes are formed on the semiconductor wafer 101. The main surface 30a of the layer 30 is attached and used. Since the bumps are formed so as to be electrically connected to the circuit formed on the semiconductor wafer, the bump forming surface 101a is a circuit surface.

In the present embodiment, the bumped semiconductor wafer is fragmented by DBG or LDBG into a plurality of semiconductor chips. That is, before and after the protective sheet for semiconductor processing is attached, after the groove is formed on the surface (circuit surface) or after the modified region is formed inside the semiconductor wafer, the protective sheet for semiconductor processing is applied to the circuit surface. The back surface of the attached semiconductor wafer, which is the surface opposite to the circuit surface, is ground.

When the semiconductor wafer is formed with irregularities such as convex electrodes, when the thickness of the semiconductor wafer is reduced by grinding, the size of the irregularities is relatively large with respect to the thickness of the semiconductor wafer. Therefore, when the unevenness is not properly embedded in the protective sheet for semiconductor processing, the following problems become more apparent by performing DBG or LDBG. That is, problems such as water infiltrating the circuit surface of the semiconductor wafer during backside grinding, chips separated after grinding move, and the chips collide with each other to cause cracks in the chips become apparent. Further, when the protective sheet for semiconductor processing is peeled off after grinding, the protective sheet for semiconductor processing is peeled off while a part of the protective sheet for semiconductor processing is attached to a plurality of semiconductor chips as adherends (glue residue is generated). The problem also becomes apparent.

Therefore, in the present embodiment, the physical characteristics of the protective sheet for semiconductor processing are controlled as follows.

(1.1 Young's modulus of protective sheet for semiconductor processing before energy ray curing at 50 ° C)
In this embodiment, the Young's modulus of the protective sheet for semiconductor processing at 50 ° C. is 600 MPa or more. When the Young's modulus is within the above range, the fragmented chips can be sufficiently held even after the wafer is fragmented. As a result, it is possible to prevent the individualized chips from moving and colliding with each other to cause cracks in the chips.

As will be described later, since the pressure-sensitive adhesive layer and the intermediate layer, which are the constituent elements of the protective sheet for semiconductor processing according to the present embodiment, are energy ray-curable, the above Young's modulus is the Young's modulus before energy ray curing. Chip cracks occur because the adhesive layer and the intermediate layer have not been cured by energy rays.

The Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50 ° C. is preferably 610 MPa or more, and more preferably 620 MPa or more.

The upper limit of the Young's modulus is not particularly specified, but is, for example, 3000 MPa from the viewpoint of the adhesiveness of the protective sheet for semiconductor processing.

In this embodiment, the Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50 ° C. is measured by a tensile test. Specifically, a tensile test is performed in accordance with JIS K 7127 (1999), and Young's modulus is calculated from tensile load, tensile strain, and the like.

The protective sheet for semiconductor processing is not limited to the configuration shown in FIG. 1A, and may have other layers as long as the effects of the present invention can be obtained. That is, as long as the base material, the intermediate layer and the pressure-sensitive adhesive layer are laminated in this order, for example, another layer may be formed between the base material and the intermediate layer, or the intermediate layer and the pressure-sensitive adhesive layer may be formed. Another layer may be formed between the and. When the protective sheet for semiconductor processing has another layer, the Young's modulus of the entire protective sheet for semiconductor processing including the other layer may be within the above range.

In particular, in the present embodiment, as shown in FIG. 1B, it is preferable that the base material has the buffer layer 40 on the main surface 30b opposite to the main surface on which the pressure-sensitive adhesive layer is formed. By having the buffer layer 40, the occurrence of the above problem can be further suppressed.

Since the buffer layer is relatively soft, it tends to reduce the Young's modulus of the protective sheet for semiconductor processing. Therefore, when the protective sheet for semiconductor processing has a buffer layer, it is necessary to adjust the Young's modulus of the protective sheet for semiconductor processing so as to be within the above range.

Hereinafter, the components of the semiconductor processing protective sheet 1 shown in FIG. 1B will be described in detail.

(2. Base material)
The base material is not limited as long as it is made of a material that can support the semiconductor wafer. For example, various resin films used as a base material for back grind tape are exemplified. The base material may be composed of a single-layer film made of one resin film, or may be made of a multi-layer film in which a plurality of resin films are laminated.

(2.1 Physical characteristics of base material)
In the present embodiment, the base material preferably has high rigidity. Due to the high rigidity of the base material, it becomes easy to keep the Young's modulus of the protective sheet for semiconductor processing within the above range. Even if the thickness of the semiconductor wafer is reduced by grinding, the wafer can be held without being damaged. Specifically, the Young's modulus of the base material is preferably 1000 MPa or more, more preferably 1500 MPa or more, and even more preferably 2000 MPa or more.

In the present embodiment, the thickness of the base material is preferably 15 μm or more and 200 μm or less, and more preferably 40 μm or more and 150 μm or less.

(2.2 Material of base material)
As the material of the base material, a material in which the Young's modulus of the base material is within the above range is preferable. In the present embodiment, for example, polyester such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, total aromatic polyester, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, biaxially stretched polypropylene and the like. Can be mentioned. Among these, polyester is preferable, and polyethylene terephthalate is more preferable.

(3. Intermediate layer)
The intermediate layer is a layer arranged between the base material and the pressure-sensitive adhesive layer. In this embodiment, the intermediate layer is energy ray curable. Therefore, before the energy ray curing, the viscoelasticity of the intermediate layer is low, so that the intermediate layer sufficiently follows the unevenness formed on the surface of the semiconductor wafer together with the pressure-sensitive adhesive layer, and the unevenness is formed into the pressure-sensitive adhesive layer and the intermediate layer. Can be embedded. As a result, even when the semiconductor wafer is ground very thinly and a force is applied to the convex electrode or the like, the pressure-sensitive adhesive layer and the intermediate layer can sufficiently protect the convex electrode or the like.

On the other hand, after the energy ray curing, not only the adhesive layer but also the intermediate layer is cured and shrunk. Therefore, even when the protective sheet for semiconductor processing is peeled off from the semiconductor wafer or the semiconductor chip after fragmentation, the elastic coefficient of the intermediate layer is increased, so that the elastic coefficient of the entire protective sheet for semiconductor processing is also improved. The pressure-sensitive adhesive layer does not easily remain attached to the semiconductor wafer or the semiconductor chip after fragmentation (glue residue is suppressed).

Further, when the convex electrode or the like penetrates the pressure-sensitive adhesive layer, the intermediate layer embeds and protects the convex electrode or the like. The intermediate layer may be composed of one layer (single layer), or may be composed of two or more layers.

The thickness of the intermediate layer 20 may be set in consideration of the size of the unevenness of the semiconductor wafer, for example, the height of the convex electrode. In the present embodiment, the thickness of the intermediate layer 20 is preferably 60 μm or more and 250 μm or less, and more preferably 100 μm or more and 200 μm or less. The thickness of the intermediate layer means the thickness of the entire intermediate layer. For example, the thickness of an intermediate layer composed of a plurality of layers means the total thickness of all the layers constituting the intermediate layer.

(3.1 Composition for intermediate layer)
Since the intermediate layer is energy ray-curable as described above, it is preferably formed from a composition having energy ray curability (composition for intermediate layer). In the present embodiment, the composition for the intermediate layer is an acrylic polymer (A) having a weight average molecular weight of 300,000 to 1.5 million and an energy ray-curable acrylic polymer having a weight average molecular weight of 50,000 to 250,000. It is preferable to contain (B). The acrylic polymer (A) is non-energy ray-curable or energy ray-curable, but in the present embodiment, it is preferably non-energy ray-curable.

In the present specification, the "weight average molecular weight" is a polystyrene-equivalent value measured by a gel permeation chromatography (GPC) method unless otherwise specified. For the measurement by such a method, for example, the high-speed GPC apparatus "HLC-8120 GPC" manufactured by Tosoh Corporation, the high-speed columns "TSK gel volume H _XL- H", "TSK Gel GMH _XL ", "TSK Gel G2000 H _XL " (The above, all manufactured by Tosoh Corporation) are connected in this order, and the detector is used as a differential refractometer under the conditions of column temperature: 40 ° C. and liquid feeding rate: 1.0 mL / min.

(3.1.1 Acrylic polymer (A))
As described above, the acrylic polymer (A) may be energy ray-curable or non-energy ray-curable. In this embodiment, the case where the acrylic polymer (A) is non-energy ray-curable will be described. (The acrylic polymer (A) is preferably a non-energy ray-curable polymer having a structural unit derived from (meth) acrylate. Specifically, the acrylic polymer (A) is an alkyl (meth). ) It is more preferable to consist of an acrylic copolymer having a structural unit derived from the acrylate (a1) and a structural unit derived from the functional group-containing monomer (a2).

As the alkyl (meth) acrylate (a1), an alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms is used. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl. (Meta) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) ) Acrylate and the like can be mentioned.

Among these, the alkyl (meth) acrylate (a1) is preferably an alkyl (meth) acrylate having an alkyl group having 4 to 8 carbon atoms. Specifically, n-butyl (meth) acrylate is preferable. The alkyl (meth) acrylate (a1) may be used alone or in combination of two or more.

The content of the structural unit derived from the alkyl (meth) acrylate (a1) in the acrylic polymer (A) is preferably 50 to 50% by mass with respect to the total structural unit (100% by mass) of the acrylic polymer (A). It is 99.5% by mass, more preferably 60 to 99% by mass, and even more preferably 80 to 95% by mass.

When this content is 50% by mass or more, the holding performance of the pressure-sensitive adhesive sheet is enhanced, and it becomes easy to improve the followability to an adherend having large irregularities. Further, if it is 99.5% by mass or less, a certain amount or more of the constituent units derived from the component (a2) can be secured.

The functional group-containing monomer (a2) is a monomer having a functional group such as a hydroxy group, a carboxy group, an epoxy group, an amino group, a cyano group, a nitrogen atom-containing ring group, and an alkoxysilyl group. Among the above, the functional group-containing monomer (a2) is preferably one or more selected from a hydroxy group-containing monomer, a carboxy group-containing monomer, and an epoxy group-containing monomer.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl ( Hydroxyalkyl (meth) acrylates such as meta) acrylate and 4-hydroxybutyl (meth) acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol can be mentioned.

Examples of the carboxy group-containing monomer include (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid.

Examples of the epoxy-containing monomer include an epoxy group-containing (meth) acrylic acid ester and a non-acrylic epoxy group-containing monomer. Examples of the epoxy group-containing (meth) acrylic acid ester include glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, (3,4-epoxycyclohexyl) methyl (meth) acrylate, and 3-epoxycyclo-2-. Examples thereof include hydroxypropyl (meth) acrylate. Examples of the non-acrylic epoxy group-containing monomer include glycidyl crotonate and allyl glycidyl ether.

The functional group-containing monomer (a2) may be used alone or in combination of two or more.

Among the functional group-containing monomers (a2), the carboxy group-containing monomer is more preferable, and (meth) acrylic acid is more preferable, and acrylic acid is most preferable. When a carboxy group-containing monomer is used as the functional group-containing monomer (a2), the cohesive force of the intermediate layer is enhanced, and the holding performance of the intermediate layer and the like can be further improved.

The content of the structural unit derived from the functional group-containing monomer (a2) in the acrylic polymer (A) is preferably 0.5 with respect to the total structural unit (100% by mass) of the acrylic polymer (A). It is ~ 40% by mass, more preferably 3 to 20% by mass, still more preferably 5 to 15% by mass.

When the content of the constituent unit derived from the component (a2) is 0.5% by mass or more, the cohesive force of the intermediate layer is high, and the compatibility with the component (B) is easily improved. On the other hand, when the content is 40% by mass or less, the constituent unit derived from the component (a1) can be secured in a certain amount or more.

The acrylic polymer (A) may be a copolymer of an alkyl (meth) acrylate (a1) and a functional group-containing monomer (a2), but the component (a1), the component (a2), and these (a2) components are used. It may be a polymer with other monomers (a3) other than the components a1) and (a2).

Examples of the other monomer (a3) include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentenyloxy. Examples thereof include (meth) acrylate having a cyclic structure such as ethyl (meth) acrylate, vinyl acetate, styrene and the like. The other monomer (a3) may be used alone or in combination of two or more.

The content of the structural unit derived from the other monomer (a3) in the acrylic polymer (A) is preferably 0 to 20% by mass with respect to the total structural unit (100% by mass) of the acrylic polymer (A). %, More preferably 0 to 10% by mass, still more preferably 0 to 5% by mass.

The weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 300,000 to 1,500,000, more preferably 400,000 to 1,100,000, and even more preferably 450,000 to 900,000. By setting Mw to these upper limit values or less, the acrylic polymer (A) has good compatibility with the acrylic polymer (B). Further, by setting Mw within the above range, it becomes easy to improve the holding performance of the adhesive sheet.

The content of the acrylic polymer (A) in the composition for the intermediate layer is preferably 40 to 95% by mass, more preferably 45 to 92% by mass, based on the total amount (100% by mass) of the composition for the intermediate layer. %, More preferably 60 to 90% by mass or more.

When the composition for the intermediate layer is diluted with a diluted solution such as an organic solvent as described later, the total amount of the composition for the intermediate layer means the total amount of the solid content excluding the diluted solution. The same applies to the composition for the pressure-sensitive adhesive layer described later.

(3.1.2 Acrylic polymer (B))
The acrylic polymer (B) is an acrylic polymer having energy ray curability by introducing an energy ray-polymerizable group. The acrylic polymer (B) has a weight average molecular weight (Mw) of 50,000 to 250,000. In the present invention, by using the component (B) in the intermediate layer, the convex electrode is sufficiently embedded when grinding the back surface of the semiconductor wafer before the energy ray curing, and the energy ray curing is performed after the grinding, thereby agglomerating the intermediate layer. Good peeling from the semiconductor chip is facilitated while preventing destruction.

The weight average molecular weight (Mw) of the acrylic polymer (B) is preferably 60,000 to 220,000, more preferably 70,000 to 200,000, and even more preferably 85,000 to 150,000.

The acrylic polymer (B) is an acrylic polymer having an energy ray-polymerizable group introduced therein and having a structural unit derived from (meth) acrylate. The energy ray-polymerizable group of the acrylic polymer (B) is preferably introduced into the side chain of the acrylic polymer. The energy ray-polymerizable group may be a group containing an energy ray-polymerizable carbon-carbon double bond, and examples thereof include a (meth) acryloyl group and a vinyl group. Among them, a (meth) acryloyl group is preferable. ..

The acrylic polymer (B) is energy ray-polymerized on an acrylic copolymer (B0) having a structural unit derived from an alkyl (meth) acrylate (b1) and a structural unit derived from a functional group-containing monomer (b2). It is preferably a reaction product obtained by reacting a polymerizable compound (Xb) having a sex group.

As the alkyl (meth) acrylate (b1), an alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms is used, and specific examples thereof include those exemplified as the component (a1). Among these, the alkyl (meth) acrylate (b1) is preferably an alkyl (meth) acrylate having an alkyl group having 4 to 8 carbon atoms. Specifically, n-butyl (meth) acrylate is preferable. In addition, they may be used individually by 1 type, and may be used in combination of 2 or more types.

The content of the structural unit derived from the alkyl (meth) acrylate (b1) in the acrylic copolymer (B0) is preferably relative to the total structural unit (100% by mass) of the acrylic copolymer (B0). It is 50 to 95% by mass, more preferably 60 to 85% by mass, and even more preferably 65 to 80% by mass. When this content is 50% by mass or more, the shape of the formed intermediate layer can be sufficiently maintained. Further, if it is 95% by mass or less, a certain amount of the structural unit derived from the component (b2) which is the reaction point with the polymerizable compound (Xb) can be secured.

The functional group-containing monomer (b2) includes a monomer having a functional group exemplified in the above-mentioned functional group-containing monomer (a2), and is selected from a hydroxy group-containing monomer, a carboxy group-containing monomer, and an epoxy group-containing monomer 1. Seeds or higher are preferred. Examples of these specific compounds include the same compounds as those exemplified as the component (a2).

Further, as the functional group-containing monomer (b2), a hydroxy group-containing monomer is preferable, and among them, various hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate are more preferable. By using the hydroxyalkyl (meth) acrylate, it becomes possible to relatively easily react the polymerizable compound (Xb) with the acrylic copolymer (B0).

Further, the functional groups in the functional group-containing monomer (a2) used in the acrylic polymer (A) and the functional group-containing monomer (b2) used in the acrylic polymer (B) are the same as each other. It may be different or may be different, but it is preferable that they are different. That is, for example, if the functional group-containing monomer (a2) is a carboxy group-containing monomer, the functional group-containing monomer (b2) is preferably a hydroxyl group-containing monomer. As described above, when the functional groups are different from each other, for example, the acrylic polymer (B) can be preferentially crosslinked by a crosslinking agent described later, and the above-mentioned adhesive sheet holding performance and the like can be improved. It will be easier to make it better.

The content of the structural unit derived from the functional group-containing monomer (b2) in the acrylic copolymer (B0) is preferably 10 with respect to the total structural unit (100% by mass) of the acrylic copolymer (B0). It is ~ 45% by mass, more preferably 15-40% by mass, still more preferably 20-35% by mass. When it is 10% by mass or more, a relatively large number of reaction points with the polymerizable compound (Xb) can be secured, and energetic polymerizable property can be easily introduced into the side chain. Further, if it is 45% by mass or less, the shape of the formed intermediate layer can be sufficiently maintained.

The acrylic copolymer (B0) may be a copolymer of an alkyl (meth) acrylate (b1) and a functional group-containing monomer (b2), but the component (b1), the component (b2), and these It may be a copolymer with other monomers (b3) other than the components (b1) and (b2).

Examples of the other monomer (b3) include those exemplified as the above-mentioned monomer (a3).

The content of the structural unit derived from the other monomer (b3) in the acrylic copolymer (B0) is preferably 0 to 0 with respect to the total structural unit (100% by mass) of the acrylic copolymer (B0). It is 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass.

The polymerizable compound (Xb) is a substituent capable of reacting with an energy ray-polymerizable group and a functional group in a structural unit derived from the component (b2) of the acrylic copolymer (B0) (hereinafter, simply "reactive substitution"). It is a compound having a "group").

Examples of the energy ray-polymerizable group include (meth) acryloyl group and vinyl group as described above, and (meth) acryloyl group is preferable. The polymerizable compound (Xb) is preferably a compound having 1 to 5 energy ray-polymerizable groups per molecule.

The reactive substituent in the polymerizable compound (Xb) may be appropriately changed according to the functional group of the functional group-containing monomer (b2), and examples thereof include an isocyanate group, a carboxyl group, and an epoxy group. An isocyanate group is preferable from the viewpoint of reactivity and the like. When the polymerizable compound (Xb) has an isocyanate group, it can easily react with the acrylic copolymer (B0), for example, when the functional group of the functional group-containing monomer (b2) is a hydroxy group. become.

Specific examples of the polymerizable compound (Xb) include (meth) acryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, (meth) acryloyl isocyanate, allyl isocyanate, and glycidyl (meth) acrylate. Examples include (meth) acrylic acid. These polymerizable compounds (Xb) may be used alone or in combination of two or more.

Among these, (meth) acryloyloxyethyl is a compound having an isocyanate group suitable as the reactive substituent and having an appropriate distance between the main chain and the energy ray-polymerizable group. Isocyanates are preferred.

The polymerizable compound (Xb) is preferably 40 to 98 equivalents, more preferably 60 to 90 equivalents, out of the total functional groups (100 equivalents) derived from the functional group-containing monomer (b2) in the acrylic polymer (B). More preferably, 70 to 85 equivalents are reacted with the functional group.

In the composition for the intermediate layer, the content of the acrylic polymer (B) is preferably 5 to 60 parts by mass, preferably 10 to 35 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). More preferably. By reducing the content of the component (B) in this way, the intermediate layer can easily follow the unevenness of the semiconductor wafer.

(3.1.3 Crosslinking agent)
The composition for the intermediate layer preferably further contains a cross-linking agent. Examples of the cross-linking agent include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an aziridine-based cross-linking agent, and a metal chelate-based cross-linking agent. Among these, an isocyanate-based cross-linking agent is preferable. When an isocyanate-based cross-linking agent is used, for example, when the component (B) has a hydroxy group, the cross-linking agent preferentially cross-links the acrylic polymer (B).

The composition for the intermediate layer is cross-linked by a cross-linking agent, for example, by heating after coating. The intermediate layer is crosslinked with an acrylic polymer, particularly a low molecular weight acrylic polymer (B), so that a coating film is appropriately formed and the intermediate layer easily exhibits a function as an intermediate layer.

The content of the cross-linking agent is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and further preferably 1 to 5 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). Is.

Examples of the isocyanate-based cross-linking agent include polyisocyanate compounds. Specific examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate. And so on. Moreover, these biuret form, isocyanurate form, and adduct form which is a reaction product with low molecular weight active hydrogen-containing compound such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil can also be mentioned.

These may be used individually by 1 type, or may be used in combination of 2 or more type. Further, among the above, a polyhydric alcohol (for example, trimethylolpropane or the like) adduct of an aromatic polyisocyanate such as tolylene diisocyanate is preferable.

Examples of the epoxy-based cross-linking agent include 1,3-bis (N, N'-diglycidyl aminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-m-xylylenediamine, and ethylene glycol. Examples thereof include diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylpropan diglycidyl ether, diglycidyl aniline, and diglycidyl amine. These may be used individually by 1 type, or may be used in combination of 2 or more type.

Examples of the metal chelate-based cross-linking agent include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium, as well as acetylacetone, ethyl acetoacetate and tris (2,4). -A compound or the like coordinated with (pentangionate) or the like can be mentioned. These may be used individually by 1 type, or may be used in combination of 2 or more type.

Examples of the aziridine-based cross-linking agent include diphenylmethane-4,4'-bis (1-aziridine carboxamide), trimethylolpropane tri-β-aziridinyl propionate, and trimethylolmethanetri-β-aziridinyl. Propionate, toluene-2,4-bis (1-aziridine carboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tris-1- (2-methylaziridine) phosphine, Examples thereof include trimethylolpropane tri-β- (2-methylaziridine) propionate and hexa [1- (2-methyl) -aziridinyl] triphosphatriazine.

(3.1.4 Photopolymerization Initiator)
The composition for the intermediate layer preferably further contains a photopolymerization initiator. Since the composition for the intermediate layer contains a photopolymerization initiator, the energy ray curing of the composition for the intermediate layer by ultraviolet rays or the like can be easily promoted.

Examples of the photopolymerization initiator include acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, Michler ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin. Isobutyl ether, benzyl diphenisulfide, tetramethylthium monosulfide, benzyl dimethyl ketal, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethane- 1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) ) -Butanone-1,2-Hydroxy-2-methyl-1-phenyl-propan-1-one, diethylthioxanthone, isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and other low molecular weight polymerization initiators , Oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone} and other oligomerized polymerization initiators. These may be used alone or in combination of two or more. Among these, 1-hydroxycyclohexylphenyl ketone is preferable.

The content of the photopolymerization initiator is preferably 1 to 10 with respect to 100 parts by mass of the acrylic polymer (A) so that curing can proceed sufficiently even with a small content of the acrylic polymer (B). It is by mass, more preferably 2 to 8 parts by mass.

The composition for the intermediate layer may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, tackifiers and the like. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). It is a mass part.

The Young's modulus of the protective sheet for semiconductor processing is, for example, when an acrylic polymer (B) is used, the type and amount of the monomers constituting the acrylic polymer (B), and the acrylic polymer (B). ) Can be adjusted by the amount of the energy ray-polymerizable group introduced into the). For example, increasing the amount of energy ray-polymerizable groups tends to increase Young's modulus. Further, it can be appropriately adjusted by the amount of the cross-linking agent blended in the intermediate layer, the amount of the photopolymerization initiator, and the like.

(4. Adhesive layer)
The pressure-sensitive adhesive layer is attached to the circuit surface of the semiconductor wafer, protects the circuit surface until it is peeled off from the circuit surface, and supports the semiconductor wafer. In this embodiment, the pressure-sensitive adhesive layer is energy ray curable. Therefore, before the energy ray curing, the pressure-sensitive adhesive layer can sufficiently follow the unevenness formed on the surface of the semiconductor wafer together with the intermediate layer, and the unevenness can be embedded in the protective sheet for semiconductor processing. As a result, even when the semiconductor wafer is ground very thinly and a force is applied to the convex electrodes or the like, the semiconductor processing protective sheet can sufficiently protect the convex electrodes or the like.

On the other hand, after the energy ray curing, the pressure-sensitive adhesive layer is cured and shrunk. Therefore, even when the protective sheet for semiconductor processing is peeled off from the semiconductor wafer or the semiconductor chip after being individualized, the adhesive layer is unlikely to be coagulated and broken, so that a part of the adhesive layer is made into the semiconductor wafer or individualized. It is difficult for it to remain attached to the later semiconductor chip (glue residue is suppressed).

Further, the pressure-sensitive adhesive layer may be composed of one layer (single layer), or may be composed of a plurality of layers of two or more layers.

The thickness of the pressure-sensitive adhesive layer is not particularly limited as long as it can sufficiently support the semiconductor wafer. In the present embodiment, the thickness of the pressure-sensitive adhesive layer is preferably 5 μm or more and 500 μm or less, and more preferably 8 μm or more and 100 μm or less. The thickness of the pressure-sensitive adhesive layer means the thickness of the entire pressure-sensitive adhesive layer. For example, the thickness of the pressure-sensitive adhesive layer composed of a plurality of layers means the total thickness of all the layers constituting the pressure-sensitive adhesive layer.

(4.1 Composition for Adhesive Layer)
Since the pressure-sensitive adhesive layer is energy ray-curable as described above, it is preferably formed from a composition having energy ray-curable property (composition for pressure-sensitive adhesive layer). In the present embodiment, the composition for the pressure-sensitive adhesive layer is preferably a composition in which the pressure-sensitive adhesive layer has a resin.

The composition for the pressure-sensitive adhesive layer contains, for example, an acrylic polymer, polyurethane, rubber-based polymer, polyolefin, silicone, or the like as a pressure-sensitive adhesive component (adhesive resin) capable of exhibiting adhesiveness in the pressure-sensitive adhesive layer. Among these, an acrylic polymer is preferable.

The composition for the pressure-sensitive adhesive layer may have energy ray-curable properties by blending an energy ray-curable compound separately from the pressure-sensitive adhesive resin, but the above-mentioned adhesive resin itself has energy ray-curable properties. Is preferable. When the adhesive resin itself has energy ray curability, an energy ray-polymerizable group is introduced into the adhesive resin, but it is preferable that the energy ray-polymerizable group is introduced into the main chain or side chain of the adhesive resin. ..

When an energy ray-curable compound is blended separately from the adhesive resin, a monomer or an oligomer having an energy ray-polymerizable group is used as the energy ray-curable compound. The oligomer is an oligomer having a weight average molecular weight (Mw) of less than 10,000, and examples thereof include urethane (meth) acrylate. Further, even when the adhesive resin itself has energy ray curability, the composition for the pressure-sensitive adhesive layer may contain an energy ray curable compound in addition to the adhesive resin.

Hereinafter, the case where the energy ray-curable adhesive resin contained in the composition for the pressure-sensitive adhesive layer is an acrylic polymer (hereinafter, also referred to as “acrylic polymer (C)”) will be described in more detail. ..

(4.1.1 Acrylic polymer (C))
The acrylic polymer (C) is an acrylic polymer having an energy ray-polymerizable group introduced therein and having a structural unit derived from (meth) acrylate. The energy ray-polymerizable group is preferably introduced into the side chain of the acrylic polymer.

The acrylic polymer (C) is energy ray-polymerized on an acrylic copolymer (C0) having a structural unit derived from an alkyl (meth) acrylate (c1) and a structural unit derived from a functional group-containing monomer (c2). It is preferably a reaction product obtained by reacting a polymerizable compound (Xc) having a sex group.

As the alkyl (meth) acrylate (c1), an alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms is used, and specific examples thereof include those exemplified as the component (a1). Among these, the alkyl (meth) acrylate (c1) is preferably an alkyl (meth) acrylate having an alkyl group having 4 to 8 carbon atoms. Specifically, 2-ethylhexyl (meth) acrylate and n-butyl (meth) acrylate are preferable, and n-butyl (meth) acrylate is more preferable. In addition, they may be used individually by 1 type, and may be used in combination of 2 or more types.

The content of the structural unit derived from alkyl (meth) acrylate (c1) in the acrylic copolymer (C0) is the acrylic copolymer (C0) from the viewpoint of improving the adhesive strength of the formed pressure-sensitive adhesive layer. It is preferably 50 to 99% by mass, more preferably 60 to 97% by mass, and further preferably 70 to 96% by mass with respect to all the constituent units (100% by mass).

For example, the alkyl (meth) acrylate (c1) may contain ethyl (meth) acrylate methyl (meth) acrylate in addition to the above 2-ethylhexyl (meth) acrylate and n-butyl (meth) acrylate. By containing these monomers, it becomes easy to adjust the adhesive performance of the adhesive layer to a desired one.

Examples of the functional group-containing monomer (c2) include monomers having a functional group exemplified as the above-mentioned functional group-containing monomer (a2), and specifically, a hydroxy group-containing monomer, a carboxy group-containing monomer, and an epoxy group-containing monomer. One or more selected from the monomers is preferable. Examples of these specific compounds include the same compounds as those exemplified as the component (a2).

As the functional group-containing monomer (c2), the hydroxy group-containing monomer is more preferable, and the hydroxyalkyl (meth) acrylate is more preferable, and 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) are more preferable. Acrylate is more preferred, and 4-hydroxybutyl (meth) acrylate is particularly preferred.

By using hydroxyalkyl (meth) acrylate as the component (c2), it becomes possible to relatively easily react the polymerizable compound (Xc) with the acrylic copolymer (C0). Further, when 4-hydroxybutyl (meth) acrylate is used, the tensile strength of the intermediate layer is increased, and it becomes easy to prevent adhesive residue.

The content of the structural unit derived from the functional group-containing monomer (c2) in the acrylic copolymer (C0) is preferably 1 with respect to the total structural unit (100% by mass) of the acrylic copolymer (C0). It is ~ 40% by mass, more preferably 2 to 35% by mass, still more preferably 3 to 30% by mass, still more preferably 10 to 30% by mass.

When the content is 1% by mass or more, a certain amount of functional groups serving as reaction points with the polymerizable compound (Xc) can be secured. Therefore, since the pressure-sensitive adhesive layer can be appropriately cured by irradiation with energy rays, it is possible to reduce the adhesive strength after irradiation with energy rays. Further, when the content is 40% by mass or less, a sufficient pot life can be ensured when the solution of the composition for the pressure-sensitive adhesive layer is applied to form the pressure-sensitive adhesive layer.

The acrylic copolymer (C0) may be a copolymer of an alkyl (meth) acrylate (c1) and a functional group-containing monomer (c2), but the component (c1), the component (c2), and these It may be a copolymer with other monomers (c3) other than the components (c1) and (c2).

Examples of the other monomer (c3) include those exemplified as the above-mentioned monomer (a3).

The content of the structural unit derived from the other monomer (c3) in the acrylic copolymer (C0) is preferably 0 to 0 with respect to the total structural unit (100% by mass) of the acrylic copolymer (C0). It is 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass.

The polymerizable compound (Xc) reacts with the energy ray-polymerizable group and the functional group in the structural unit derived from the component (c2) of the acrylic copolymer (C0), similarly to the above-mentioned polymerizable compound (Xb). It is a compound having a possible substituent (reactive substituent), and preferably a compound having 1 to 5 energy ray-polymerizable groups per molecule.

Specific examples of the reactive substituent and the energy ray-polymerizable group are the same as those of the polymerizable compound (Xb). Therefore, the reactive substituent is preferably an isocyanate group, and the energy ray-polymerizable group is a (meth) acryloyl group. preferable.

In addition, examples of the specific polymerizable compound (Xc) include those similar to those exemplified as the above-mentioned polymerizable compound (Xb), and (meth) acryloyloxyethyl isocyanate is preferable. The polymerizable compound (Xc) may be used alone or in combination of two or more.

The polymerizable compound (Xc) is preferably 30 to 98 equivalents, more preferably 40 to 95 equivalents, out of the total functional groups (100 equivalents) derived from the functional group-containing monomer (c2) in the acrylic copolymer (C0). Is reacted with a functional group.

The weight average molecular weight (Mw) of the acrylic polymer (C) is preferably 10,000 to 1,500,000, more preferably 250,000 to 1,000,000, and even more preferably 350,000 to 800,000. Having such Mw makes it possible to impart appropriate adhesiveness to the pressure-sensitive adhesive layer.

Even when the adhesive resin has energy ray curability, the composition for the pressure-sensitive adhesive layer preferably contains an energy ray curable compound other than the adhesive resin. As such an energy ray-curable compound, a monomer or oligomer which has an unsaturated group in the molecule and can be polymerized and cured by energy ray irradiation is preferable.

Specifically, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,4-butylene glycol di (meth). Polyvalent (meth) acrylate monomers such as acrylates and 1,6-hexanediol (meth) acrylates, oligomers such as urethane (meth) acrylates, polyester (meth) acrylates, polyether (meth) acrylates, and epoxy (meth) acrylates. Can be mentioned.

Among these, urethane (meth) acrylate oligomers are preferable from the viewpoint of having a relatively high molecular weight and not easily lowering the elastic modulus of the pressure-sensitive adhesive layer.

(4.1.2 Cross-linking agent)
The composition for the pressure-sensitive adhesive layer preferably further contains a cross-linking agent. The composition for the pressure-sensitive adhesive layer is cross-linked by a cross-linking agent, for example, by heating after coating. In the pressure-sensitive adhesive layer, the acrylic polymer (C) is crosslinked by a cross-linking agent, so that a coating film is appropriately formed and the pressure-sensitive adhesive layer easily exhibits a function as a pressure-sensitive adhesive layer.

Examples of the cross-linking agent include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an aziridine-based cross-linking agent, and a chelate-based cross-linking agent. Among these, an isocyanate-based cross-linking agent is preferable. The cross-linking agent may be used alone or in combination of two or more. Specific examples of the isocyanate-based cross-linking agent include those exemplified as a cross-linking agent that can be used in the composition for the intermediate layer, and the same applies to preferred compounds thereof.

The content of the cross-linking agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 7 parts by mass, and further preferably 0.3 to 4 parts by mass with respect to 100 parts by mass of the acrylic polymer (C). It is a mass part.

(4.1.3 Photopolymerization Initiator)
The composition for the pressure-sensitive adhesive layer preferably further contains a photopolymerization initiator. Examples of the photopolymerization initiator include those exemplified as the photopolymerization initiator used in the above-mentioned composition for the intermediate layer. The photopolymerization initiator may be used alone or in combination of two or more. Among the above, 2,2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexylphenyl ketone are preferable.

The content of the photopolymerization initiator is preferably 0.5 to 15 parts by mass, more preferably 1 to 12 parts by mass, and further preferably 4.5 to 10 parts by mass with respect to 100 parts by mass of the acrylic polymer (C). It is a mass part.

The composition for the pressure-sensitive adhesive layer may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes and the like. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.02 to 2 parts by mass with respect to 100 parts by mass of the acrylic polymer (C). It is a mass part.

The Young's modulus of the protective sheet for semiconductor processing is, for example, when an acrylic polymer (C) is used, the type and amount of the monomers constituting the acrylic polymer (C), and the acrylic polymer (C). ) Can be adjusted by the amount of the energy ray-polymerizable group introduced into the). For example, increasing the amount of energy ray-polymerizable groups tends to increase Young's modulus. Further, it can be appropriately adjusted by the amount of the cross-linking agent blended in the pressure-sensitive adhesive layer, the amount of the photopolymerization initiator, and the like.

(5. Buffer layer)
As shown in FIG. 1B, the buffer layer is formed on the main surface opposite to the main surface of the base material on which the pressure-sensitive adhesive layer is formed. The buffer layer 40 is a layer that is softer than the base material, and relaxes the stress at the time of backside grinding of the semiconductor wafer to prevent cracks and chips from occurring in the semiconductor wafer. Further, the semiconductor wafer to which the protective sheet for semiconductor processing is attached is arranged on the vacuum table via the protective sheet for semiconductor processing at the time of backside grinding, but by having a buffer layer as a constituent layer of the protective sheet for semiconductor processing. , Easy to be properly held on the vacuum table.

The thickness of the buffer layer is preferably 1 to 100 μm, more preferably 5 to 80 μm, and even more preferably 10 to 60 μm. By setting the thickness of the buffer layer within the above range, the buffer layer can appropriately relieve stress during backside grinding.

The buffer layer may be a layer formed from a composition for a buffer layer containing an energy ray-polymerizable compound, a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, or ethylene / (meth) acrylic. It may be a film such as an acid copolymer film, an ethylene / (meth) acrylic acid ester copolymer film, an LDPE film, and an LLDPE film.

The base material having a buffer layer is obtained by laminating a buffer layer on one side or both sides of the base material.

(5.1 Composition for buffer layer)
The composition for a buffer layer containing an energy ray-polymerizable compound can be cured by being irradiated with energy rays.

Further, the composition for a buffer layer containing an energy ray-polymerizable compound is more specifically polymerizable with urethane (meth) acrylate (d1) and an alicyclic group or a heterocyclic group having 6 to 20 ring-forming atoms. It preferably contains the compound (d3). Further, the composition for a buffer layer may contain a polyfunctional polymerizable compound (d2) and / or a polymerizable compound having a functional group (d4) in addition to the above components (d1) and (d3). Moreover, the composition for a buffer layer may contain a photopolymerization initiator in addition to the above-mentioned components. Further, the composition for a buffer layer may contain other additives and resin components as long as the effects of the present invention are not impaired.

Hereinafter, each component contained in the composition for a buffer layer containing an energy ray-polymerizable compound will be described in detail.

(5.1.1 Urethane (meth) acrylate (d1))
The urethane (meth) acrylate (d1) is a compound having at least a (meth) acryloyl group and a urethane bond, and has a property of polymerizing and curing by irradiation with energy rays. Urethane (meth) acrylate (d1) is an oligomer or polymer.

The weight average molecular weight (Mw) of the component (d1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and even more preferably 3,000 to 20,000. The number of (meth) acryloyl groups (hereinafter, also referred to as “functional number”) in the component (d1) may be monofunctional, bifunctional, or trifunctional or higher, but is preferably monofunctional or bifunctional. ..

The component (d1) can be obtained, for example, by reacting a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound with a polyhydric isocyanate compound with a (meth) acrylate having a hydroxyl group. The component (d1) may be used alone or in combination of two or more.

The polyol compound used as a raw material for the component (d1) is not particularly limited as long as it is a compound having two or more hydroxy groups. It may be any of a bifunctional diol, a trifunctional triol, and a tetrafunctional or higher functional polyol, but a bifunctional diol is preferable, and a polyester type diol or a polycarbonate type diol is more preferable.

Examples of the polyisocyanate compound include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; isophorone diisocyanate, norbornan diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and dicyclohexylmethane-2. , 4'-diisocyanate, ω, ω'-diisocyanate Diisocyanate, alicyclic diisocyanates such as dimethylcyclohexane; 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, trizine diisocyanate, tetramethylene xylylene diisocyanate, naphthalene- Examples thereof include aromatic diisocyanates such as 1,5-diisocyanate.

Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferable.

Urethane (meth) acrylate (d1) can be obtained by reacting a (meth) acrylate having a hydroxy group with a terminal isocyanate urethane prepolymer obtained by reacting the above-mentioned polyol compound with a polyhydric isocyanate compound. The (meth) acrylate having a hydroxy group is not particularly limited as long as it is a compound having a hydroxy group and a (meth) acryloyl group in at least one molecule.

Specific examples of the (meth) acrylate having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 4-hydroxycyclohexyl (meth). Acrylate, 5-hydroxycyclooctyl (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, pentaerythritol tri (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, etc. Hydroxyalkyl (meth) acrylate; hydroxy group-containing (meth) acrylamide such as N-methylol (meth) acrylamide; Reaction obtained by reacting diglycidyl ester of vinyl alcohol, vinylphenol, bisphenol A with (meth) acrylic acid. Things; etc.

Among these, hydroxyalkyl (meth) acrylate is preferable, and 2-hydroxyethyl (meth) acrylate is more preferable.

The conditions for reacting the terminal isocyanate urethane prepolymer and the (meth) acrylate having a hydroxy group are preferably conditions of reacting at 60 to 100 ° C. for 1 to 4 hours in the presence of a solvent and a catalyst added as necessary. ..

The content of the component (d1) in the composition for the buffer layer is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and further, based on the total amount (100% by mass) of the composition for the buffer layer. It is preferably 25 to 55% by mass.

(5.1.2 Polyfunctional polymerizable compound (d2))
The polyfunctional polymerizable compound refers to a compound having two or more photopolymerizable unsaturated groups. The photopolymerizable unsaturated group is a functional group containing a carbon-carbon double bond, and examples thereof include a (meth) acryloyl group, a vinyl group, an allyl group, and a vinylbenzyl group. Two or more photopolymerizable unsaturated groups may be combined. The photopolymerizable unsaturated group in the polyfunctional polymerizable compound reacts with the (meth) acryloyl group in the component (d1), or the photopolymerizable unsaturated group in the component (d2) reacts with each other. A three-dimensional network structure (crosslinked structure) is formed. When a polyfunctional polymerizable compound is used, the crosslinked structure formed by energy ray irradiation increases as compared with the case where a compound containing only one photopolymerizable unsaturated group is used, so that the buffer layer is unique. It exhibits viscoelasticity and makes it easy to relieve stress during backside grinding.

Although the definition of the component (d2) overlaps with the definitions of the component (d3) and the component (d4) described later, the overlapping part is included in the component (d2). For example, a compound having an alicyclic group or a heterocyclic group having 6 to 20 ring-forming atoms and having two or more (meth) acryloyl groups is included in the definitions of both the component (d2) and the component (d3). However, in the present invention, the compound is included in the component (d2). Further, a compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group or an amino group and having two or more (meth) acryloyl groups is included in the definitions of both the component (d2) and the component (d4). In the present invention, the compound is included in the component (d2).

From the above viewpoint, the number of photopolymerizable unsaturated groups (number of functional groups) in the polyfunctional polymerizable compound is preferably 2 to 10 and more preferably 3 to 6.

The weight average molecular weight of the component (d2) is preferably 30 to 40,000, more preferably 100 to 10000, and even more preferably 200 to 1000.

Specific components (d2) include, for example, diethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 1,6-hexane. Didioldi (meth) acrylate, trimethylolpropantri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, divinylbenzene, vinyl (meth) acrylate , Divinyl adipate, N, N'-methylenebis (meth) acrylamide and the like. Among these, dipentaerythritol hexa (meth) acrylate is preferable. The component (d2) may be used alone or in combination of two or more.

The content of the component (d2) in the composition for the buffer layer is preferably 2 to 40% by mass, more preferably 3 to 20% by mass, and further, based on the total amount (100% by mass) of the composition for the buffer layer. It is preferably 5 to 15% by mass.

(5.1.3 Polymerizable compound having an alicyclic group or a heterocyclic group having 6 to 20 ring-forming atoms (d3))
The component (d3) is a polymerizable compound having an alicyclic group or a heterocyclic group having 6 to 20 ring-forming atoms, and more preferably a compound having at least one (meth) acryloyl group. It is preferably a compound having one (meth) acryloyl group. By using the component (d3), the film-forming property of the obtained composition for a buffer layer can be improved.

Although the definition of the component (d3) and the definition of the component (d4) described later overlap with each other, the overlapping part is included in the component (d4). For example, a compound having at least one (meth) acryloyl group, an alicyclic group or heterocyclic group having 6 to 20 ring-forming atoms, and a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group is a component. Although included in the definitions of both (d3) and component (d4), the compound is included in component (d4) in the present invention.

Specific components (d3) include, for example, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxy (meth) acrylate, cyclohexyl (meth) acrylate, and the like. Alicyclic group-containing (meth) acrylates such as adamantan (meth) acrylate; heterocyclic group-containing (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate and morpholine (meth) acrylate; and the like can be mentioned. The component (d3) may be used alone or in combination of two or more.

Among the alicyclic group-containing (meth) acrylates, isobornyl (meth) acrylates are preferable, and among the heterocyclic group-containing (meth) acrylates, tetrahydrofurfuryl (meth) acrylates are preferable.

The content of the component (d3) in the composition for the buffer layer is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and further, based on the total amount (100% by mass) of the composition for the buffer layer. It is preferably 25 to 55% by mass.

The content ratio of the component (d2) to the component (d3) in the buffer layer composition [(d2) / (d3)] is preferably 0.1 to 3.0, more preferably 0.15. It is ~ 2.0, more preferably 0.18 ~ 1.0.

(5.1.4 Polymerizable compound having a functional group (d4))
The component (d4) is a polymerizable compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, and an amino group, and more preferably a compound having at least one (meth) acryloyl group. It is preferably a compound having one (meth) acryloyl group.

The component (d4) has good compatibility with the component (d1), and it becomes easy to adjust the viscosity of the buffer layer composition within an appropriate range. Further, even if the buffer layer is made relatively thin, the buffer performance is improved.

Examples of the component (d4) include a hydroxyl group-containing (meth) acrylate, an epoxy group-containing compound, an amide group-containing compound, and an amino group-containing (meth) acrylate. Among these, hydroxyl group-containing (meth) acrylate is preferable.

Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxy. Examples thereof include butyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, phenylhydroxypropyl (meth) acrylate, and 2-hydroxy-3-phenoxypropyl acrylate. Among these, a hydroxyl group-containing (meth) acrylate having an aromatic ring such as phenylhydroxypropyl (meth) acrylate is more preferable. The component (d4) may be used alone or in combination of two or more.

The content of the component (d4) in the composition for the buffer layer is preferably 5 with respect to the total amount (100% by mass) of the composition for the buffer layer in order to improve the film forming property of the composition for the buffer layer. It is ~ 40% by mass, more preferably 7 to 35% by mass, still more preferably 10 to 30% by mass.

The content ratio [(d3) / (d4)] of the component (d3) to the component (d4) in the composition for the buffer layer is preferably 0.5 to 3.0, more preferably 1.0. ~ 3.0, more preferably 1.3 to 3.0.

(5.1.5 Polymerizable compounds other than the components (d1) to (d4) (d5))
The composition for forming a buffer layer may contain other polymerizable compounds (d5) other than the above-mentioned components (d1) to (d4) as long as the effects of the present invention are not impaired.

Examples of the component (d5) include alkyl (meth) acrylates having an alkyl group having 1 to 20 carbon atoms; styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam and the like. Vinyl compounds: and the like. The component (d5) may be used alone or in combination of two or more.

The content of the component (d5) in the composition for the buffer layer is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, still more preferably 0 to 5% by mass, and particularly preferably 0 to 2% by mass. Is.

(5.1.6 Photopolymerization Initiator)
The composition for a buffer layer preferably further contains a photopolymerization initiator from the viewpoint of shortening the polymerization time by light irradiation and reducing the amount of light irradiation when forming the buffer layer.

Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanosen compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amine and quinone. Specifically, for example, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfate, etc. Examples thereof include tetramethylthiuram monosulfide, azobisisobutyrolnitrile, dibenzyl, diacetyl, 8-chloranthraquinone, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide and the like. These photopolymerization initiators can be used alone or in combination of two or more.

The content of the photopolymerization initiator in the composition for the buffer layer is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the total amount of the energy ray-polymerizable compounds. Parts, more preferably 0.3 to 5 parts by mass.

(5.1.7 Other additives)
The composition for the buffer layer may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes and the like. When these additives are blended, the content of each additive in the buffer layer composition is preferably 0.01 to 6 parts by mass, based on 100 parts by mass of the total amount of the energy ray-polymerizable compound. It is preferably 0.1 to 3 parts by mass.

The buffer layer formed from the composition for a buffer layer containing an energy ray-polymerizable compound is obtained by polymerizing and curing the composition for a buffer layer having the above composition by irradiation with energy rays. That is, the buffer layer is a cured composition for the buffer layer.

Therefore, the buffer layer preferably contains a polymerization unit derived from the component (d1) and a polymerization unit derived from the component (d3). Further, the buffer layer may contain a polymerization unit derived from the component (d2) and / or a polymerization unit derived from the component (d4), or may contain a polymerization unit derived from the component (d5). good. The content ratio of each polymerization unit in the buffer layer usually corresponds to the ratio (charge ratio) of each component constituting the composition for the buffer layer.

(6. Release sheet)
A release sheet may be attached to the surface of the protective sheet for semiconductor processing. Specifically, the release sheet is attached to the surface of the pressure-sensitive adhesive layer of the protective sheet for semiconductor processing. The release sheet is attached to the surface of the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer during transportation and storage. The release sheet is detachably attached to the protective sheet for semiconductor processing, and before the protective sheet for semiconductor processing is used (that is, before attaching the wafer), it is peeled off from the protective sheet for semiconductor processing and removed.

As the release sheet, a release sheet in which at least one surface has been peeled is used, and specific examples thereof include a release sheet coated with a release agent on the surface of the base material for the release sheet.

A resin film is preferable as the base material for the release sheet, and examples of the resin constituting the resin film include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, polypropylene resin, and polyethylene resin. Examples thereof include the polyolefin resin of. Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.

The thickness of the release sheet is not particularly limited, but is preferably 10 to 200 μm, more preferably 20 to 150 μm.

(7. Manufacturing method of protective sheet for semiconductor processing)
The method for producing a protective sheet for semiconductor processing according to the present embodiment is a method capable of forming an intermediate layer and an adhesive layer on one main surface of a base material and forming a buffer layer on the other main surface of the base material. If this is the case, the present invention is not particularly limited, and a known method may be used.

First, as a composition for forming the intermediate layer, for example, a composition for an intermediate layer containing the above-mentioned components, or a composition obtained by diluting the composition for an intermediate layer with a solvent or the like is prepared. Similarly, as the composition for the pressure-sensitive adhesive layer for forming the pressure-sensitive adhesive layer, for example, a composition for a pressure-sensitive adhesive layer containing the above-mentioned components, or a composition obtained by diluting the composition for the pressure-sensitive adhesive layer with a solvent or the like. Prepare things. Similarly, as a buffer layer composition for forming a buffer layer, for example, a buffer layer composition containing the above-mentioned components or a composition obtained by diluting the pressure-sensitive adhesive layer composition with a solvent or the like is prepared. do.

Examples of the solvent include organic solvents such as methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol and isopropanol.

Then, a composition for a buffer layer is applied to the peeled surface of the first peeling sheet by a spin coating method, a spray coating method, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, etc. A coating film is formed by coating by a known method described above, and the coating film is semi-cured to form a buffer layer film on a release sheet. The buffer layer film formed on the release sheet is attached to the base material, and the buffer layer film is completely cured to form the buffer layer.

In the present embodiment, the coating film is preferably cured by irradiation with energy rays. Further, the coating film may be cured by a single curing treatment or may be performed in a plurality of times.

Subsequently, the composition for an intermediate layer is applied to the peeling-treated surface of the second release sheet by a known method and heat-dried to form an intermediate layer on the second release sheet. Then, the intermediate layer on the second release sheet and the surface of the base material on which the buffer layer is not formed are bonded together to remove the second release sheet.

Subsequently, the composition for the pressure-sensitive adhesive layer is applied to the peel-processed surface of the third release sheet by a known method, and heat-dried to form the pressure-sensitive adhesive layer on the third release sheet. Then, by laminating the pressure-sensitive adhesive layer and the intermediate layer on the third release sheet, the intermediate layer and the pressure-sensitive adhesive layer are formed on one main surface of the base material in this order, and the other main surface of the base material is formed. A protective sheet for semiconductor processing having a buffer layer formed on the surface can be obtained. The third release sheet may be removed when the protective sheet for semiconductor processing is used.

(8. Manufacturing method of semiconductor device)
The protective sheet for semiconductor processing according to the present invention is preferably used in DBG when it is attached to the surface of a semiconductor wafer and the back surface of the wafer is ground. In particular, the protective sheet for semiconductor processing according to the present invention is preferably used for LDBG in which a chip group having a small calf width can be obtained when a semiconductor wafer is fragmented.

As a non-limiting example of the protective sheet for semiconductor processing, a method for manufacturing a semiconductor device will be described in more detail below.

Specifically, the method for manufacturing a semiconductor device includes at least the following steps 1 to 4.
Step 1: The above-mentioned protective sheet for semiconductor processing is attached to the surface of a semiconductor wafer having irregularities. Step 2: A groove is formed from the front surface side of the semiconductor wafer, or the semiconductor wafer is formed from the front surface or the back surface of the semiconductor wafer. Step of forming a modified region inside Step 3: A semiconductor wafer on which a protective sheet for semiconductor processing is attached to the front surface and the groove or modified region is formed is ground from the back surface side to form a groove or modified region. Step 4: A step of peeling a protective sheet for semiconductor processing from a semiconductor wafer (that is, a plurality of semiconductor chips) that has been fragmented.

Hereinafter, each step of the method for manufacturing the semiconductor device will be described in detail.

(Step 1)
In step 1, the protective sheet for semiconductor processing according to the present embodiment is attached to the surface of the semiconductor wafer having irregularities via an adhesive layer. Since the protective sheet for semiconductor processing according to the present embodiment has the above-mentioned characteristics, it can sufficiently follow the unevenness and embed it to protect it.

This step may be performed before the step 2 described later, but may be performed after the step 2. For example, when forming a modified region on a semiconductor wafer, it is preferable to perform step 1 before step 2. On the other hand, when a groove is formed on the surface of the semiconductor wafer by dicing or the like, step 1 is performed after step 2. That is, the protective sheet for semiconductor processing is attached to the surface of the wafer having the groove formed in the step 2 described later in the main step 1.

The semiconductor wafer used in this production method may be a silicon wafer, a wafer such as gallium arsenic, silicon carbide, lithium tantalate, lithium niobate, gallium nitride, indium phosphorus, or a glass wafer. .. The thickness of the semiconductor wafer before grinding is not particularly limited, but is usually about 500 to 1000 μm. Further, a semiconductor wafer usually has a circuit formed on its surface. The circuit can be formed on the wafer surface by various methods including a conventionally used method such as an etching method and a lift-off method. In particular, in the present embodiment, convex electrodes (bumps) are formed on the circuit surface of the semiconductor wafer. As a result, the circuit surface of the semiconductor wafer has irregularities as compared with the semiconductor wafer on which the convex electrodes are not formed. The height of the convex electrode is not particularly limited, but is usually 5 to 200 μm.

(Step 2)
In step 2, a groove is formed from the front surface side of the semiconductor wafer, or a modified region is formed inside the semiconductor wafer from the front surface or the back surface of the semiconductor wafer.

The groove formed in this step is a groove having a depth shallower than the thickness of the semiconductor wafer. The groove can be formed by dicing using a conventionally known wafer dicing apparatus or the like. Further, the semiconductor wafer is divided into a plurality of semiconductor chips along the groove in step 3 described later.

Further, the modified region is a brittle portion of the semiconductor wafer, and the semiconductor wafer is destroyed by grinding in the grinding process, the semiconductor wafer becomes thin, or a force due to grinding is applied, and the semiconductor chip is destroyed. This is the area that serves as the starting point for individualization. That is, in step 2, the groove and the modified region are formed along the dividing line when the semiconductor wafer is divided and separated into semiconductor chips in step 3, which will be described later.

The modified region is formed by irradiating a laser focused on the inside of the semiconductor wafer, and the modified region is formed inside the semiconductor wafer. The laser irradiation may be performed from the front surface side or the back surface side of the semiconductor wafer. In the embodiment of forming the modified region, when the step 2 is performed after the step 1 and the laser irradiation is performed from the wafer surface, the semiconductor wafer is irradiated with the laser via the semiconductor processing protective sheet.

A semiconductor wafer to which a protective sheet for semiconductor processing is attached and a groove or a modified region is formed is placed on a chuck table and is attracted to and held by the chuck table. At this time, the surface side of the semiconductor wafer is arranged on the table side and is adsorbed.

(Step 3)
After the steps 1 and 2, the back surface of the semiconductor wafer on the chuck table is ground to separate the semiconductor wafer into a plurality of semiconductor chips.

Here, when the groove is formed on the semiconductor wafer, the back surface grinding is performed so as to thin the semiconductor wafer at least to a position reaching the bottom of the groove. By this backside grinding, the groove becomes a notch penetrating the wafer, and the semiconductor wafer is divided by the notch and individualized into individual semiconductor chips.

On the other hand, when a modified region is formed, the ground surface (back surface of the wafer) may reach the modified region by grinding, but it does not have to reach the modified region strictly. That is, the semiconductor wafer may be ground to a position close to the modified region so that the semiconductor wafer is broken and separated into semiconductor chips starting from the modified region. For example, the actual individualization of the semiconductor chip may be performed by attaching the pip-up tape described later and then stretching the pip-up tape.

Further, after the back surface grinding is completed, dry polishing may be performed prior to picking up the chips.

The shape of the individualized semiconductor chip may be a square shape or an elongated shape such as a rectangle. The thickness of the fragmented semiconductor chip is not particularly limited, but is preferably about 5 to 100 μm, and more preferably 10 to 45 μm. A modified region is provided inside the wafer with a laser, and the wafer is fragmented by stress during grinding of the back surface of the wafer. According to LDBG, the thickness of the fragmented semiconductor chip is 50 μm or less, more preferably 10. It becomes easy to make it ~ 45 μm. The size of the fragmented semiconductor chip is not particularly limited, but the chip size is preferably ^{less than 600 mm 2} , more preferably less than 400 mm ² , and even more preferably less than ^{120 mm 2.}

When the protective sheet for semiconductor processing according to the present embodiment is used, even with such a thin and / or small semiconductor chip, at the time of backside grinding (step 3) and at the time of peeling off the protective sheet for semiconductor processing (step 4). It is prevented that the semiconductor chip is cracked.

(Step 4)
Next, the protective sheet for semiconductor processing is peeled off from the fragmented semiconductor wafer (that is, a plurality of semiconductor chips). This step is performed by, for example, the following method.

In the present embodiment, since the intermediate layer and the pressure-sensitive adhesive layer of the protective sheet for semiconductor processing are formed of an energy ray-curable pressure-sensitive adhesive, the intermediate layer and the pressure-sensitive adhesive layer are cured and shrunk by irradiating with energy rays to be coated. It reduces the adhesive strength to the adherend (individualized semiconductor wafer). Next, a pickup tape is attached to the back surface side of the fragmented semiconductor wafer, and the position and direction are adjusted so that the pickup can be picked up. At this time, the ring frame arranged on the outer peripheral side of the wafer is also attached to the pick-up tape, and the outer peripheral edge portion of the pickup tape is fixed to the ring frame. The wafer and the ring frame may be attached to the pickup tape at the same time, or may be attached at different timings. Next, the protective sheet for semiconductor processing is peeled off from the plurality of semiconductor chips held on the pickup tape.

Since the protective sheet for semiconductor processing according to the present embodiment has the above-mentioned characteristics, good peeling can be performed without remaining adhering to unevenness, particularly convex electrodes.

After that, a plurality of semiconductor chips on the pickup tape are picked up and fixed on a substrate or the like to manufacture a semiconductor device.

The pickup tape is not particularly limited, but is composed of, for example, a base material and a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer provided on one surface of the base material.

The example of using the protective sheet for semiconductor processing according to the present invention in a method of individualizing a semiconductor wafer by DBG or LDBG has been described above, but the protective sheet for semiconductor processing according to the present invention is a piece of a semiconductor wafer. It can be preferably used for LDBGs in which a group of chips having a small calf width and a thinner chip can be obtained when the wafer is formed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

Hereinafter, the invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The measurement method and evaluation method in this example are as follows.

(Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50 ° C)
At 50 ° C., the protective sheet for semiconductor processing before energy ray curing produced in Examples and Comparative Examples was subjected to a tensile test at a test speed of 200 mm / min in accordance with JIS K 7127 (1999), and Young's modulus was measured. ..

(DBG chip crack evaluation)
A pre-dicing method in which a groove is formed from the wafer surface of a silicon wafer having a diameter of 12 inches, a protective sheet for semiconductor processing produced in Examples and Comparative Examples is attached to the wafer surface, and the wafer is separated by back grinding. The chips were separated into chips with a thickness of 50 μm and a chip size of 5 mm square. After that, without peeling off the protective sheet for semiconductor processing, the corners of the chips separated from the wafer ground surface were observed with a digital microscope (product name "VHX-1000", manufactured by KEYENCE), and the presence or absence of cracks in each chip was observed. Was observed, the crack occurrence rate in 700 chips was measured, and evaluated according to the following evaluation criteria.
A: less than 1.0%, B: 1.0 to 2.0%, C: more than 2.0%

(LDBG chip crack evaluation)
A protective sheet for semiconductor processing produced in Examples and Comparative Examples was attached to a silicon wafer having a diameter of 12 inches and a thickness of 775 μm using a tape laminator for back grind (manufactured by Lintec Corporation, device name “RAD-3510F / 12”). bottom. A lattice-shaped modified region was formed on the wafer using a laser saw (manufactured by Disco Corporation, device name "DFL7361"). The grid size was 5 mm × 5 mm.

Next, using a back surface grinding device (manufactured by Disco Corporation, device name "DGP8761"), grinding (including dry polishing) was performed until the thickness became 50 μm, and the wafer was fragmented into a plurality of chips.

After the grinding process, energy rays (ultraviolet rays) were irradiated, and a dicing tape (Adwill D-176 manufactured by Lintec Corporation) was attached to the opposite surface of the protective sheet for semiconductor processing, and then the protective sheet for semiconductor processing was peeled off. After that, the individualized chips were observed with a digital microscope (product name "VHX-1000", manufactured by KEYENCE), the cracked chips were counted, the crack occurrence rate in 700 chips was measured, and the following evaluation criteria were used. Evaluated in.
A: less than 1.0%, B: 1.0 to 2.0%, C: more than 2.0%

(Bump absorption evaluation)
A wafer with spherical bumps (8-inch wafer, manufactured by Waltz) made of Sn-3Ag-0.5Cu alloy having a bump height of 80 μm, a pitch of 200 μm, and a diameter of 100 μm, and protected for semiconductor processing produced in the following Examples and Comparative Examples. The sheet was attached using a laminator (product name "RAD-3510F / 12", manufactured by Lintec Corporation). At the time of sticking, the temperature of the laminating table and the laminating roll of the apparatus was set to 50 ° C.

After laminating, the diameter of the circular void formed around the bump from the base material side was measured using a digital optical microscope (product name "VHX-1000", manufactured by KEYENCE).

The smaller the diameter of the gap, the higher the bump absorption of the protective sheet for semiconductor processing. The superiority or inferiority of bump absorption was judged from the following criteria.
◯: The diameter of the void is less than 150 μm.
X: The diameter of the void is 150 μm or more.

(Evaluation of adhesive residue on bumps)
A wafer with spherical bumps (8-inch wafer, manufactured by Waltz) made of Sn-3Ag-0.5Cu alloy having a bump height of 80 μm, a pitch of 200 μm, and a diameter of 100 μm, and protected for semiconductor processing produced in the following Examples and Comparative Examples. The sheet was attached using a laminator (product name "RAD-3510F / 12", manufactured by Lintec Corporation). At the time of sticking, the temperature of the laminating table and the laminating roll of the apparatus was set to 50 ° C.

After laminating, UV was irradiated from the semiconductor processing protective sheet side at an irradiation speed of 15 mm / sec with a UV irradiation device (product name "RAD-2000 m / 12", manufactured by Lintec Corporation). Next, the protective sheet for semiconductor processing was peeled from the evaluation wafer using a wafer mounter (product name "RAD-2700F / 12", manufactured by Lintec Corporation) under the conditions of a peeling speed of 4 mm / sec and a temperature of 40 ° C. Using an electron microscope (product name "VE-9800", manufactured by KEYENCE), observe the part where the bumps on the adhesive layer surface of the protective sheet for semiconductor processing after peeling were embedded from an observation angle of 45 °, and apply the adhesive. It was confirmed whether the layer was broken.

The superiority or inferiority of the adhesive residue was judged from the following criteria.
A: No breaks (no adhesive residue).
B: There is a break (with adhesive residue).

(Example 1)
(1) Base material A PET film with a double-sided easy-adhesion layer (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd., thickness: 50 μm, Young's modulus at 23 ° C.: 2550 MPa) was prepared as a base material.

(2) Buffer layer (synthesis of urethane acrylate-based oligomer)
A urethane acrylate-based oligomer (UA-1) having a weight average molecular weight (Mw) of about 5000 by reacting 2-hydroxyethyl acrylate with a terminal isocyanate urethane prepolymer obtained by reacting a polyester diol with isophorone diisocyanate. Got

(Preparation of composition for buffer layer)
50 parts by mass of the urethane acrylate-based oligomer (UA-1) synthesized above, 40 parts by mass of isobornyl acrylate (IBXA), and 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate (HPPA) are further blended. A composition for a buffer layer containing 1.0 part by mass of 2-hydroxy-2-methyl-1-phenyl-propane-1-one (manufactured by BASF Japan, product name "Irgacure 1173") as a photopolymerization initiator. Was prepared.

(Creation of base material with buffer layer)
The composition for a buffer layer was applied to the peel-treated surface of another release sheet (manufactured by Lintec Corporation, trade name "SP-PET38131") to form a coating film. Next, the coating film was irradiated with ultraviolet rays, and the coating film was semi-cured to form a buffer layer forming film having a thickness of 53 μm.

For the above ultraviolet irradiation, a belt conveyor type ultraviolet irradiation device (manufactured by Eye Graphics, device name "US2-0801") and a high-pressure mercury lamp (manufactured by Eye Graphics, device name "H08-L41") are used. The irradiation was performed under irradiation conditions of a lamp height of 230 mm, an output of 80 mW / cm, an illuminance of 90 mW / cm ^{2 with} a light wavelength of 365 nm, and an irradiation amount of 50 mJ / cm ^2.

Then, the surface of the formed buffer layer forming film and the base material are bonded to each other, and ultraviolet rays are irradiated again from the release sheet side on the buffer layer forming film to completely cure the buffer layer forming film, and the thickness is 53 μm. A buffer layer was formed. The above-mentioned ultraviolet irradiation uses the above-mentioned ultraviolet irradiation device and high-pressure mercury lamp, and irradiates with a lamp height of 220 mm, a conversion output of 120 mW / cm ^{, an illuminance of 160 mW / cm 2 with} a light wavelength of 365 nm, and an irradiation amount of 650 mJ / cm ² . It was performed under the conditions.

(3) Non-energy ray-curable acrylic copolymer (a) (Mw:) obtained by copolymerizing 91 parts by mass of n-butyl acrylate (BA) and 9 parts by mass of acrylic acid (AA) as a base material with an intermediate layer. 600,000) was obtained.

Obtained by copolymerizing 62 parts by mass of n-butyl acrylate (BA), 10 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA) separately from the acrylic copolymer (a). 2-methacryloyloxyethyl isocyanate (MOI) is reacted with the acrylic polymer so as to add 80 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to the energy ray-curable acrylic. The system copolymer (b) (Mw: 100,000) was obtained.

To 100 parts by weight of this non-energy ray-curable acrylic copolymer (a), 13 parts by weight of the energy ray-curable acrylic copolymer (b) was added, and an isocyanate-based cross-linking agent (Tosoh Co., Ltd.) was added as a cross-linking agent. 2.79 parts by weight of product name "Coronate L") was added, 3.71 parts by weight of 1-hydroxycyclohexylphenylketone (BASF, Irgacure184) was added as a photoinitiator, and solid content was added using toluene. The concentration was adjusted to 37%, and the mixture was stirred for 30 minutes to prepare the composition for the intermediate layer.

Next, the prepared solution of the intermediate layer composition was applied to a PET-based release film (SP-PET381031 thickness 38 μm manufactured by Lintec Corporation) and dried to form an intermediate layer having a thickness of 55 μm. This is adhered to the opposite surface of the surface of the base material with the buffer layer on which the buffer layer is formed, and the solution of the composition for the intermediate layer is further applied on a PET-based release film (SP-PET381031 manufactured by Lintec Corporation, thickness 38 μm). This was repeated a total of 3 times to form a base material with an intermediate layer having a thickness of 165 μm.

(4) Adhesive layer (preparation of composition for adhesive layer)
An acrylic polymer obtained by copolymerizing 52 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA) was added to an acrylic polymer. 2-Methacryloyloxyethyl isocyanate (MOI) is reacted so as to be added to 90 equivalents of all hydroxyl groups (100 equivalents), and an energy ray-curable acrylic copolymer (c) (Mw: 500,000) ) Was obtained.

In 100 parts by mass of this energy ray-curable acrylic copolymer (c), 12 parts by mass of polyfunctional urethane acrylate (manufactured by Mitsubishi Chemical Co., Ltd., Shikou UT-4332), which is an energy ray-curable compound, and an isocyanate-based cross-linking agent (Made by Toso, product name "Coronate L") 1.1 parts by mass, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide as a photopolymerization initiator (BASF, EnergyTPO) ) Was blended in an amount of 1 part by mass and diluted with methyl ethyl ketone to prepare a coating liquid for a pressure-sensitive adhesive layer composition having a solid content concentration of 34% by mass.

(Manufacturing of protective sheet for semiconductor processing)
The peeling-treated surface of the peeling sheet (manufactured by Lintec Corporation, trade name "SP-PET38131") is coated with the coating liquid of the adhesive layer composition obtained above, heat-dried, and thickened on the peeling sheet. A pressure-sensitive adhesive layer having a size of 10 μm was formed.

Then, the pressure-sensitive adhesive layer was bonded to the surface on which the intermediate layer of the base material with the intermediate layer was formed to prepare a protective sheet for semiconductor processing. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

(Example 2)
A buffer layer was formed using the following composition for a buffer layer, and a protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the thickness of the intermediate layer was 120 μm. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

50 parts by mass of urethane acrylate-based oligomer (UA-1), 40 parts by mass of isobornyl acrylate (IBXA), 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate (HPPA), and pentaerythritol triacrylate (PETA) 10. Blended by mass, and further blended 1.0 part by mass of 2-hydroxy-2-methyl-1-phenyl-propane-1-one (manufactured by BASF Japan, product name "Irgacure 1173") as a photopolymerization initiator. Then, a composition for forming a buffer layer was prepared.

(Example 3)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the thickness of the intermediate layer was 240 μm. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

(Example 4)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the base material with a buffer layer of Example 1 was changed to the following base material with a buffer layer. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

A low density polyethylene film (thickness: 27.5 μm) was prepared as a buffer layer.
The buffer layer was laminated on both sides of the substrate used in Example 1 by a dry laminating method to obtain a substrate with a buffer layer laminated in the order of LDPE / PET / LDPE.

(Example 5)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the base material with a buffer layer of Example 1 was changed to the PET base material of Example 1. That is, no buffer layer is formed on the base material. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

(Comparative Example 1)
The base material with a buffer layer of Example 1 was changed to an EVA film base material (Funkrea LEAG120 manufactured by Gunze Co., Ltd.), and the amount of the acrylic copolymer (b) added to the intermediate layer composition was changed to 67 parts by mass. A protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the thickness of the intermediate layer was set to 100 μm and the following composition for the pressure-sensitive adhesive layer was used as the composition for the pressure-sensitive adhesive layer. That is, no buffer layer is formed on the base material. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

It was obtained by copolymerizing 70 parts by mass of n-butyl acrylate (BA), 15 parts by mass of i-butyl acrylate (iBA), 5 parts by mass of methyl methacrylate (MMA), and 10 parts by mass of 4-hydroxybutyl acrylate (4HBA). 2-methacryloyloxyethyl isocyanate (MOI) is reacted with an acrylic polymer so as to add 90 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to an energy ray-curable acrylic polymer. The copolymer (d) (Mw: 500,000) was obtained.

To 100 parts by mass of this energy ray-curable acrylic copolymer (d), 1.8 parts by mass of an isocyanate-based cross-linking agent (manufactured by Toso Co., Ltd., product name "Coronate L"), 2,2 as a photopolymerization initiator. 7.29 parts by mass of −dimethoxy-2-phenylacetophenone (manufactured by BASF, Irgacure 651) was blended and diluted with toluene to prepare a coating solution of a pressure-sensitive adhesive composition having a solid content concentration of 25% by mass.

(Comparative Example 2)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the following composition for the pressure-sensitive adhesive layer was used as the composition for the pressure-sensitive adhesive layer using the base material with an intermediate layer prepared as follows. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

Base material with intermediate layer 40 parts by mass (solid content ratio) of monofunctional urethane acrylate, 45 parts by mass (solid content ratio) of isobonyl acrylate (IBXA) and 15 parts by mass (solid content ratio) of hydroxypropyl acrylate (HPA) , Pentaerythritol tetrakis (3-mercaptobutyrate) (product name "Karensu MT PE1", manufactured by Showa Denko Co., Ltd., secondary tetrafunctional thiol-containing compound, solid content concentration 100% by mass) in an amount of 3.5 parts by mass (solid). (Separation ratio), 1.8 parts by mass of UV-reactive thermal cross-linking agent, and 2-hydroxy-2-methyl-1-phenyl-propane-1-one (product name "DaroCure 1173", BASF) as a photopolymerization initiator. The UV curable resin composition prepared by blending 1.0 part by mass (100% by mass of solid content concentration) was placed on a polyethylene terephthalate (PET) film-based release film (SP-PET381031 manufactured by Lintec Co., Ltd., thickness 38 μm). The coating was applied by a die method so that the thickness after curing was 400 μm. Then, the semi-cured layer was formed by irradiating ultraviolet rays from the coating film side.

For ultraviolet irradiation, a belt conveyor type ultraviolet irradiation device (product name "ECS-401GX", manufactured by Eye Graphics Co., Ltd.) is used as the ultraviolet irradiation device, and a high-pressure mercury lamp (H04-L41 eye graphics company) is used as the ultraviolet source. The irradiation was carried out under the conditions of an illuminance of 112 mW / cm ^{2 with} a light wavelength of 365 nm and a light amount of 177 mJ / cm ² (measured with "UVPF-A1" manufactured by Eye Graphics Co., Ltd.).

A polyethylene terephthalate (PET) film (Toray's Lumirror 75U403, thickness 75 μm) is laminated on the formed semi-cured layer, and further ultraviolet irradiation is performed from the PET film side (using the above ultraviolet irradiation device and ultraviolet source, illuminance as an irradiation condition. 271 mW / cm ² ) and light amount 1200 mJ / cm ² ) were carried out and completely cured to form an intermediate layer having a thickness of 400 μm on the PET film of the base material.

Acrylic obtained by copolymerizing 60 parts by mass of 2-ethylhexyl acrylate (2EHA), 15 parts by mass of ethyl acrylate (EA), 5 parts by mass of methyl methacrylate (MMA), and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA). 2-methacryloyloxyethyl isocyanate (MOI) is reacted with the polymer so as to be added to 60 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer, and the energy ray-curable acrylic copolymer weight is applied. A coalescence (e) (Mw: 500,000) was obtained.

To 100 parts by mass of this energy ray-curable acrylic copolymer (e), 1.2 parts by mass of an isocyanate-based cross-linking agent (manufactured by Toso Co., Ltd., product name "Coronate L"), 2,2 as a photopolymerization initiator. 7.29 parts by mass of −dimethoxy-2-phenylacetophenone (manufactured by BASF, Irgacure 651) was blended and diluted with toluene to prepare a coating solution of a pressure-sensitive adhesive composition having a solid content concentration of 25% by mass.

(Comparative Example 3)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the composition for the intermediate layer did not contain the acrylic copolymer (b). Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

(Comparative Example 4)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1 except that the thickness of the intermediate layer was 300 μm. Table 1 shows the types of base materials, the composition and thickness of the intermediate layer and the pressure-sensitive adhesive layer.

The above measurements and evaluations were performed on the obtained samples (Examples 1 to 5 and Comparative Examples 1 to 4). The results are shown in Table 2.

From Table 2, when the Young's modulus of the protective sheet for semiconductor processing is within the above-mentioned range and the intermediate layer contains a UV-curable compound, the wafer having irregularities is fragmented by DBG and LDBG. Even in this case, it was confirmed that the unevenness was sufficiently embedded, the crack generation rate due to the chip shift was low, and both the embedding property of the bump and the peeling property from the bump were compatible.

1 ... Protective sheet for semiconductor processing 10 ... Base material 20 ... Intermediate layer 30 ... Adhesive layer 40 ... Buffer layer

Claims (6)

A protective sheet for semiconductor processing having a base material and an intermediate layer and an adhesive layer on one main surface of the base material in this order.
The intermediate layer and the pressure-sensitive adhesive layer are energy ray-curable and
A protective sheet for semiconductor processing in which the Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50 ° C. is 600 MPa or more. The protective sheet for semiconductor processing according to claim 1, which has a buffer layer on the other main surface of the base material. The protective sheet for semiconductor processing according to claim 1 or 2, wherein the Young's modulus of the base material is 1000 MPa or more. The protective sheet for semiconductor processing according to any one of claims 1 to 3, wherein the thickness of the intermediate layer is 60 μm or more and 250 μm or less. Claims 1 to 4 used by being attached to the surface of a semiconductor wafer in a step of grinding the back surface of a semiconductor wafer having grooves formed on the surface of the semiconductor wafer and separating the semiconductor wafer into semiconductor chips by the grinding. The protective sheet for semiconductor processing described in any of the above. A step of attaching the protective sheet for semiconductor processing according to any one of claims 1 to 5 to the surface of a semiconductor wafer having irregularities, and
A step of forming a groove from the front surface side of the semiconductor wafer, or a step of forming a modified region inside the semiconductor wafer from the front surface or the back surface of the semiconductor wafer.
A semiconductor wafer on which the protective sheet for semiconductor processing is attached to the front surface and the groove or the modified region is formed is ground from the back surface side, and the groove or the modified region is used as a starting point to form a plurality of chips. The process of individualizing and
A method for manufacturing a semiconductor device, comprising a step of peeling the protective sheet for semiconductor processing from an individualized semiconductor chip.

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